Firing a fresh salvo at Vietnam, China said bilateral trade will suffer if it allows last week's anti-China unrest to escalate.

The violence, which saw foreign businesses damaged and looted and at least two Chinese nationals killed, "has hurt the Chinese people's feelings and affected the confidence of Chinese and Vietnamese enterprises", said the Commerce Ministry's head of foreign trade Zhang Ji.

"This would definitely damage the healthy development of Sino-Vietnam trade, which China does not want to see, and will also be detrimental to the Vietnamese economy," he said, in response to a question at a briefing on new measures to boost trade.

Anti-China sentiments flared in Vietnam after Beijing deployed an oil rig in a part of the South China Sea that Hanoi also claims. On Sunday, Beijing suspended some unspecified bilateral exchanges with Hanoi.

Zhang pointed out yesterday that China has been Vietnam's biggest trading partner for the past decade. Bilateral trade last year reached US$65.5 billion (S$80 billion), a 30 per cent year-on-year increase. Some 28 per cent of Vietnam's total imports are from China, while exports to China make up 10 per cent of its total exports. By comparison, Vietnam's imports and exports form only a fraction of China's total.

Zhang said the healthy state of bilateral trade was a result of "common efforts" and had "not been easy to achieve".

Also in Beijing yesterday, former ambassador to Singapore and Thailand Zhang Jiuhuan appeared at a dialogue organised by the All-China Journalists Association on the past and future of the South China Sea issue.

He dismissed comparisons between Vietnam's anti-China riots and China's 2012 anti-Japan riots, which erupted after Japan bought three of the disputed Diaoyu/Senkaku islands from a private owner. He said Chinese authorities had not condoned the violence and acted swiftly to stop it, while the Vietnamese government adopted a hands-off policy at first.

Zhang, now vice-president of the China Public Diplomacy Association, said South China Sea claimants Vietnam, the Philippines, Malaysia and Brunei staked their claims only in the 1970s and 1980s after realising it was an oil-rich area.